Poly-enolic organic compounds used to modify physical properties of thermoplastic polymers



Patented May 8, 1951 POLY-ENOLIC ORGANIC COMPOUNDS USED TO MODIFY PHYSICAL PROPERTIES OF THERMOPLASTIC POLYMERS Edward L. Kropa, Old Greenwich, Conn., assignor to American Cyanainid Company, New York, N. Y., a corporation of Maine No Drawing. Application July 25, 1947, Serial No. 763,765

1 Claim. 1

This invention relates to thermoplastic polymeric materials and more particularly, to a process for modifying the physical properties of thermoplastic polymeric materials.

Thermoplastic polymers and, in fact, almost any particular type of resin, possesses for a given use or application certain properties which are advantageous and certain other tain so-called advantageous properties might make a resin suitable for an application wherein the corresponding set of so-called disadvantageous properties is immaterial. On the other hand, however, in many cases the disadvantageous properties will interfere with the benefits desired from the advantageous properties.

To take a. specific example, polystyrene may be considered. Polystyrene has good electrical properties and therefore should be extremely useful in the manufacture of molded articles for use in electrical equipment. Moreover, polystyrene is transparent, readily colored, relatively strong and easily molded and it should therefore find Wide use in the manufacture of various novelties and household articles. However,' polystyrene has relatively poor heat resistance and as a result of this property its application in the fields just mentioned has necessarily been somewhat limited. For example, in man electrical applications of molded plastics there is a possibility of exposure to relatively high temperatures as a result of heat generated in resistance coils and heat generated by electronic tubes, batteries, etc. Similarly, household articles of molded polystyrene are necessarily often exposed to temperatures at least as high as boiling water. Unfortunately, if articles molded of polystyrene are subjected to even moderately high temperatures they become distorted either because of internal strains if they have been injection molded or as a result of subjection to any load while at an elevated temperature. As described in the copending application of Murray G. Sturrock and Thomas Lawe, Serial No. 563,453 filed November 1 1, 1944, now abandon-ed, it has been found that polymers of dimethyl styrenes have improved heat resistance over that of polystyrene itself. They are therefore suitable for use in electrical equipment or in the manufacture of household articles for which polystyrene itself has not been entirely satisfactory.

According to the present invention I have discovered a process according to which styrene, monoalkyl substituted'styrenes and monohalogen substituted styrenes may be polymerized to produce a polymeric material of modified physical properties and particularly, a polymeric properties which are'disadvantageous. Thus, a set of cer-' styrene of improved heat resistance comparable to the polymerized dimethyl styrenes.

Another specific example of thermoplastic polymeric materials to which the present invention may be applied consists of the p'olyacrylates, i. e., polymerized acrylic and alkac'rylic acids, esters thereof, acrylonitrile, acrylamide, etc. Polyacrylates tend to be rubbery products and hence cannot be used satisfactorily in certain applications for which this property makes them unsuited. A polyacrylate of improved toughness and increased tensile strength may, however, be prepared according to my invention.

According to the present invention, therefore, I have discovered that when certain vinyl compounds are polymerized in accordance therewith the very nature of the polymer itself is changed and greatly increased molecular weights with consequent improved mechanical properties are obtained.

It is an object, therefore, of the present invention to provide a process for modifying the physical properties of thermoplastic polymers such-as polystyrenes, polyacrylates, etc.

Another object of the present invention is to provide an improved process for the polymerization of monomeric compounds containing a single polymerizable CH2=C group to produce polymeric materials soluble in organic solvents.

A further object of the present invention is to bring about polymerization of a monomeric substance containing a single polymerizable CH2=C group under such conditions that physical properties other than solubility in organic solvents of the resulting polymer are modified.

The above and other objects are attained by polymerizing at least one monomeric substance containing a single polymerizable CH2=C group in a non-acidic aqueous medium in the presence of a peroxide polymerization catalyst and in the presence of a compound containing two or three on groups.

The invention will be described in greater detail in conjunction with the following specific examples in which proportions are given in parts by weight.

Example 1 '75 parts of styrene (steam distilled from a 2% sodium hydroxide solution) 0.375 part of polyvinyl alcohol (type A, high viscosity, #R. H. 490) 0.15 part of benzoyl peroxide 0.0225 part of resorcinol 730 parts of distilled Water 3 The polyvinyl alcohol is dissolved in the water by stirring at room temperature for about 15 minutes followed by heating on a steam bath. The solution is then filtered and introduced into 0.02 part of potassium persulfate 0.0225 part of resorcinol 730 parts of distilled water The procedure of Example 1 is followed and a vessel equipped with a reflux condenser, a 5

polystyrene in the form of beads of good 00101 is thelmemeter i l m i P atmosobtained. The polymer has a Staudinger mophere of carbon dioxide is provlded by mtroduclecular Weight of 000 and moldings made men of the gas l P a of t condenser therefrom while slightly hazy are of good c0101. The benzeyl perexlde dlssolvel m the i If polystyrene is prepared in accordance with room temperature the l i 1S m the general process of Example 1 but without any filtered, and the filtered solution introduced modifying compound the polymeric product is into the vessel containing ofdpoly' normally highly discolored and it has a Staudino e control figures will facilitate evaluation of the re- 85 C. for 24 hours and then steamed to remove 16 Sums Obtained in the preceding examples any unpolymerized monomer. The styrene polymer which is obtained in the form of very slightly Example 4 discolored beads is refined by collecting on a filter 100 parts of ethyl acrylate and washing by suspension in 4 volumes Ice 25 parts of a 10% aqueous solution of Aquarex D water. The temperature of the water is raised to 20 0025 part of potassium persulfate (01% aqueous room temperature by allowing the suspension to solution) stand and finally brought up to about 75-80 C. 001 part of resorcmol by heating on a steam bath. The polystyrene is 150 parts of distilled water filtered, the refining procedure is repeated twice, 1A D t f th It f If t a 0 Q 2|. C 1 S0 1 m e e the final polymer 15 men dried 85 '1nono% s te l s 01' a l iit use 0f higher re a a lc ho is, eiu n In a vacuum oven for 48 hours. The extensive lauryl and myristyl derivatives, and is neutral in reaction. refining process is necessary for substantial The resorcinol is mixed with the ethyl acrylate mom} of an occluded pelyvmyl aleehel from the and this mixture along with the other ingredipolystyrene. ents listed above is placed in a vessel equipped Thepolymer obtained by the preeess described" with a reflux condenser and means for agitation. above calculated to have Steudmger moleeu' The reaction mixture is heated on a. steam bath Weight 32 nieldllgs made there with stirring. Polymerization starts in about 5 mm ale eny E y hee ere minutes and is complete in 15 minutes. After Example 2 35 about 30 minutes the reaction mixture is steamed to remove all volatile material and then filtered The Preeeeure of Example 15 followed except cooled and coagulated with methanol The 00- that chmethyl dihydroresorcinol is substituted agulated polymer is Washed free of emulsify for the resorcinol. Polystyrene in the form of ma agent anddried in an oven at 1000 C for beads of good color is obtained. The polymer has 1611 Ours The polymer obtained has a stau'din a Staudinger molecular weight of 70,000, and the 40 ger m ole'cul ar weight of 693 000 moldings made therefrom are clear and of good The general procedure of iflxa'mple 4 is remab color Exam 1e 3 ed with variations in the type and amount of p dispersing agent, the amount of catalyst and the 75 parts of styrene (steam distilled from a 2% type and. amount of modifying compound used, sodium hydroxide solution) Id other proportions, etc., being kept constant. 1.5 parts of polyvinyl alcohol (type E, medium The results obtained, including those of Example viscosity, #R. H. 349) 4, for the sake of completeness, are summarized 0.15 part of benzoyl peroxide in the following table.

Dispersing Agents Modifying Compound T- F1 555555: t 55155 Typo Parts Type Parts Toluene I P 1 Aqugrcx I) 10% aqueous gig? rcsorlcinc-l 1511(3)" 1 $33, 3.03 o (o f 3.54 25 0. 02; ..do 0. 03 3515" 1,385,000 41.2 a 71 25 0.025 .do.. 0.05 4154" 1,500,000 44.7 3.80 25 0.025 do 0.1 3017" 1,420, 000 42.2 5.74 25 0.025 resglil cinol monornethyl 0.02 2745 29.8 73.39

I. Sodium l1ydroxystearatc 2.5 0.025 res onsinnl 0.02 1845" 20.2 "3.00 Duponol 10% 25 1 0.05 3524" 38.1 3.54 52 52 832 it?? it 3:53 25 0: 05 27' 7" 20:2 3137 25 0.05 is 0" 12.4 2.05 25 .005 1221" 13.5 2.58 25 .01 was" 15.7 2.75 25 .004 5'17" 8. 91 2.10 25 .008 1528" 10.0 2.51 25 .015 14'3" 15.1 2.71 25 0.015 1557" 17.1 2. s4 25 .02 13/55" 15.0 2.70 25 0.015 2510" 27.1 3. 20 25 0.05 3227" 54.9 3. 55 25 0.1 3015" 30.0 3.66 25 0.2 37'42" 40.5 3. 25 0.3 47"1" 50.6 3.92 25 0.4 4501" 50.0 3.01 25 0.5 45 35" 40.0. a. 88 25 0. 02 1122" 12.2 2. 40 25 .025 dimelthyl dihydro resorci- 0.02 3633" 39.0 3. 67

In order to facilitate evaluation of the results listed in the table, it should be noted that if ethyl acrylate is polymerized according to the procedure of Example 4, but without any modifying compound present the time flow of a 1% solution of the polymer in toluene is about 2 minutes and its Staudinger molecular weight is in the neighborhood of 60,000.

The modifying effects of the compounds containing two or three C=COH groups in the process of the present invention are only obtainable if polymerization is carried out in a nonacidic aqueous medium. Thus, the monomeric materials containing a single polymerizable CH2=C group may be polymerized in neutral or alkaline aqueous dispersions or emulsions.

In the former case, suitable dispersing agents which may be used include talc, calcium phosphate, styrene-maleic acid heteropolymers, dimethyl styrene-maleic acid heteropolymers, methyl cellulose, methyl starch, glycol cellulose, gums, polyacrylamide, etc.

In the latter case it must be borne in mind that since the aqueous medium must be neutral or alkaline, cationic emulsifying agents are unsuitable. Neutral or anionic emulsifiers which may be used include, for example, sodium hydroxystearate, the sodium salts of long-chain sulfated alcohols such as sodium lauryl sulfate, the sodium salts of organic sulfonates including the sodium salts of alkyl substituted naphthalene sulfonic acids, the sodium salts of the alkyl esters of sulfosuccinic acid such as the sodium salt of the dioctyl ester of sulfosuccinic acid, etc. Mixtures of the various emulsifying agents may be used if desired.

Monomeric substances containing a single polymerizable CH2=C group which may be polymerized according to the process of the present invention to produce a soluble thermoplastic polymer of modified physical properties include, in addition to the styrene and ethyl acrylate of the specific examples, monoalkyl substituted styrenes such as the ortho-, metaand para-methyl styrenes, the ortho-, metaand para-ethyl styrenes, the ortho-, meta-, and parapropyl styrenes, etc. The alkyl substituent may contain, in general, from 1 to 6 carbon atoms. Monohalogenated styrenes such as the ortho-, metaand para-chlorostyrenes, the ortho-, metaand para-bromostyrenes, etc., may also be used. Alkyl esters of acrylic acid having from 1 to 6 carbon atoms in the alkyl group such as methyl acrylate, propyl acrylate, isobutyl acrylate, hexyl acrylate, etc., fall within the scope of the present invention as do the corresponding alkyl esters of methacrylic acid and other alkacrylic acids having from 1 to 6 carbon atoms in the alkyl group of the ester portion of the compound and from 1 to 3 carbon atoms in the alkyl group of the acid portion of the molecule, acrylic acid itself, methacrylic acid and ethacrylic acid. acrylonitrile, acrylamide, methylol acrylamide, methylol methacrylamide, methacrylamide, N-alkyl acrylamides, di-N-alkyl acrylamides, vinyl esters such as vinyl chloride, vinyl acetate, etc. Mixtures containing two, three, eight, eleven or an infinite number of monomeric substances, each containing only a single polymerizable Cl-Iz=C group, may be polymerized according to the process of the present invention which is therefore applicable to the improvement of such useful copolymers as those of acrylamide and acrylic acid esters, of acrylonitrile and acrylic acid esters, of styrene and acrylonitrile, of styrene, acrylonitrile and acrylate, etc.

Organic compounds containing two or three hydroxyl groups are generally suitable for use as modifying compounds in the process of the present invention. Examples of such compounds include dihydric phenols such as catechol, tertiary butyl catechol, resorcinol,hydroquinone; trihydric phenols such as pyrogallol, phloroglucinol, tannic acid; and other compounds containing two or three hydroxyl groups such as dimethyldihydroresorcinol, acetonyl acetone, etc. is interesting to note that of the aromatic compounds, those possessing ,a meta substitution are by far the most eifective.

The invention is not limited to the use of any particular peroxide catalyst and those which are suitable include inorganic peroxides, such as hydrogen peroxide, alkali metal'persulfates, percarbonates, perborates, etc., as potassium persulfate, sodium percaroonate, potassium perborate, etc. These catalysts are water-soluble and. may suitably be incorporated in the aqueous phase of the polymerizable emulsions or dispersions. Organic peroxides suitable for use which include benzoyl peroxide, benzoyl acetic peroxide, lanroyl peroxide, oleic peroxida'stearic peroxide, acetic peroxide, etc., are preferably incorporated in the non-aqueous phase. Mixtures of two or more, up to and including an infinite number, of the catalysts may be used, certain combinations of catalysts favoring particular physical forms of polymers.

Relatively small proportions of polymerization catalysts are used and, in general, from 0.01% to 5% thereof based on the Weight of polymerizable material is sufficient to increase the rate of polymeriaation of the monomer and in conjunction with the proper amounts of modifying compound to produce a desired property modification in accordance with the present invention. I prefer limiting the amount of catalyst to from 0.01% to 2% in usual cases, however, for practical reasons.

The particular amount of modifying compound used according to the process of the present invention is largely dependent upon the amount of peroxide catalyst present and upon the nature of the monomeric substance to be polymerized. In the polymerization of styrene, for example, as in Examples 1 through 3, an ideal combination appears to consist of about 0.2% catalyst and 0.03% modifying compound in which case the ratio of modifying compound to catalyst is 0.15. Similarly, it has been demonstrated that excellent results can be obtained in the polymerization of ethyl aerylate if the ratio of modifying compound to catalyst ranges all the Way from 0.1 to 20.0. Generally, it will be undesirable from a practical standpoint to use much more modifying compound than catalyst and, while the ratio of modifying compound to catalyst of from 0.1 to 20.0 is operable, I prefer somewhat more restrictedv ranges. For example, using from between 0.01% to 2% catalyst and operating with styrene and a di-hydroxy compound, satisfactory results are obtained when the ratio of modifying compound to catalyst is from 0.1 to 0.2. Polymerizing acrylates in the presence of di-hydroxy compounds can take place satisfactorily when the ratio of di-hydroxy compound to catalyst is from about 0.1 to 10, while use of a tri-hydroxy compound to promote polymerization of an acrylate necessitates the use of at least a ratio of 0.6, the upper limit to the range being about 12.0. It

should be understood, however, that these figures are merely preferred embodiments of the present invention with regard to specific promoting compound and specific monomeric substances which it isldesired to polymerize, and the invention in its broad sense is not limited to these particular figures but rather, only generally, to a ratio within the range of from 0.1 to 20.0.

The thermoplastic polymers prepared according to the process of the present invention are soluble in organic solvents and possess unique properties, largely occasioned by the increased molecular weights, which render them admirably suited for many applications.

The time of flow of a 1% solution in toluene of the polymers of the specific examples is determined by dissolving 1 gram of the dry polymer in 10000. of toluene at 25 C. 10 cc. of this solution are then placed in a viscosimeter tube #100 and-its time of flow determined at 25 C.

From the time flow figure, the relative viscosity maybe obtained. It is equal to where N1 is the relative viscosity and c is the concentration in grams per 100 cc. of solvent may be calculated.

The Staudinger molecular weight is calculated in the usual manner, making use of the equation: eat

where Nsp is the specific viscosity, 0 is the concentration, Km is a characteristic constant, and M is the molecular weight.

I claim:

A process for modifying the physical properties of a homopolymer of ethyl acrylate which comprises polymerizing monomeric ethyl acrylate in a non-acidic aqueous medium in the presence of from 0.015% to 0.5% by weight of phloroglucinol and 0.025% by weight of peroxide polymerization catalyst, whereby a homopolymer of V ethyl acrylate of greatly increased molecular REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS 

